title: Influence of scaffold stiffness on subchondral bone and subsequent cartilage regeneration in an ovine model of osteochondral defect healing.
abstract: BACKGROUND
  In osteochondral defects, subchondral bone, as a load-bearing structure, is believed to be important for bone and cartilage regeneration.
  
  
  OBJECTIVE
  A stiff scaffold creates better conditions for bone formation and cartilage regeneration than does a softer one.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Critical osteochondral defects were created in the femoral condyles of 24 sheep. Subchondral bone was reconstructed with a stiff scaffold or a modified softer one, with untreated defects serving as controls. The repair response was evaluated with mechanical, histological, and histomorphometrical techniques at 3 and 6 months postoperatively.
  
  
  RESULTS
  The elastic modulus of regenerated fibrocartilage over the stiff scaffold tended to be higher than in the soft scaffold group (61% vs 46% of healthy cartilage) at 3 months. No difference was determined at 6 months; all were well below healthy cartilage. Treated defects showed substantial degradation of the soft scaffold with surrounding sclerotic bone at 3 and 6 months. In contrast, degradation of the stiff scaffold was slower and occurred together with continuous osseous replacement.
  
  
  CONCLUSIONS
  Stiff scaffolds were found to improve bone regeneration. In contrast, soft scaffolds provided less support, and consequently subchondral bone became sclerotic. Although regenerated cartilage formed over the stiff scaffolds at 3 months, and these exhibited better mechanical properties than did the soft scaffold group, the mechanical properties in both treated groups were the same at 6 months, not dissimilar to that of tissue formed in the untreated specimens and inferior to native articular cartilage.
  
  
  CONCLUSIONS
  The results imply that subchondral defect filling in clinical settings advances bone regeneration and should have a comparable stiffness to that of healthy subchondral bone rather than being too flexible. Degradation of resorbable materials and consequently the loss of stiffness may compromise the healing of critical defects.
authors.affiliation: Julius Wolff Institut and Center for Musculoskeletal Surgery, Charité-Universitätsmedizin, Berlin, Germany.
authors.forename: Karin
authors.initials: K
authors.lastname: Schlichting
authors.forename: Hanna
authors.initials: H
authors.lastname: Schell
authors.forename: Ralf U
authors.initials: RU
authors.lastname: Kleemann
authors.forename: Alexander
authors.initials: A
authors.lastname: Schill
authors.forename: Andreas
authors.initials: A
authors.lastname: Weiler
authors.forename: Georg N
authors.initials: GN
authors.lastname: Duda
authors.forename: Devakara R
authors.initials: DR
authors.lastname: Epari
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001861:Bone Regeneration; D002356:Cartilage / Q000293:injuries* / Q000502:physiology; D055119:Elastic Modulus; D005260:Female; D007150:Immunohistochemistry; D007718:Knee Injuries / Q000473:pathology / Q000628:therapy*; D007719:Knee Joint / Q000473:pathology; D011098:Polyglactin 910; D012756:Sheep; D054457:Tissue Scaffolds
chemical_list: D011098:Polyglactin 910